Electronic-scan antenna

ABSTRACT

In an electronic scan modular antenna system operating at frequency F, a circuit supplies the n modules (where n is an integer) forming the antenna with n respective synchronization signals. The circuit comprises wave generating means supplying two component signals in phase quadrature in respect of each other, of frequency f F/p (where p is an integer), respective means varying respectively the amplitudes of said component signals as functions of the desired direction of radiation of the antenna beam axis, an adder forming the sum of the output signals of the amplitude varying means, n respective fixed gain attenuating means for attenuating said sum, n adding means for respectively adding the n output signals of said n attenuating means with one of said components, and multiplying means coupled respectively to the adding means outputs and supplying said synchronization signals.

United States Patent Salmon Jan. 22, 1974 ELECTRONIC-SCAN ANTENNA [75] inventor: Jacques Salmon, Paris, France ABSTRACT 73 Assignee; Thomas.CSF Paris, France In an electronic scan modular antenna system operat ing at frequency F, a circuit supplies the n modules [22] F'led: selfl- 1971 (where n is an integer) forming the antenna with n {21] Appl. No.; 179,428 respective synchronization signals. The circuit comprises wave generating means supplying two component signals in phase quadrature in respect of each Foreign pp Priority Data other, of frequency f=Flp (where p is an integer), re-

Sept. H, 1970 France 7033096 spective means varying respectively the amplitudes of said component signals as functions of the desired di- [52] US. Cl 343/100 SA rection of radiation of the antenna beam axis, an [5 l Int. Cl. H0111 3/26 adder forming the sum of the output signals of the am- [58] Field of Search 343/100 SA, 854; 323/121 plitude varying means, n respective fixed gain attenuating means for attenuating said sum, n adding means [56] References Cited for respectively adding the n output signals of said n UNITED STATES PATENTS attenuating means with one of said components, and 3.329.397 7/1967 Preble 343/:00 SA multiplying mans mupled respectively to the adding 3.022.459 2/1962 Alper 323/121 means and Supplying said synchwnizam" Pn'mary ExaminerBenjamin A. Borchelt Assistant Examiner-Denis H. McCabe Attorney, Agent, or FirmCushman et al.

nals.

6 Claims, 8 Drawing Figures ELECTRONIC-SCAN ANTENNA The present invention relates to electronic-scan antennas using active modules.

It is well known that such antennas comprise a plurality of elements or modules of identical structure, each including in particular at least one microwave power generator element, such as an elementary oscillator or amplifier, and that it is necessary to supply these with respective low-power reference signals having an identical frequency but respective different phases.

These reference signals are obtained from a single initial signal and as many variable phase-shift devices (phaseshifters or diode logic systems) as there are modules, associated with as many phase control circuits and a phase computer.

In known devices, the phaseshift devices must cover the full range of phase variation (2 17) of the radiator elements of the modules with which they are associated. In the case of directional antennas, where the beam has to scan a substantial sector, say of 90, this results in very high cost equipment as soon as the number of modules is great (currently this number is for example 100 and even more).

It is an object of the present invention to reduce the complexity of the phase control arrangement.

According to the invention there is provided an electronic scan antenna system comprising n modules Mi (i =l,2 ...n) and a circuit supplying the modules with n respective reference signals Si of frequency F said circuit comprising:

means for supplying a first and a second component signals of identical frequencyFIfl/p, where p is an integer greater than one, said signals being in phase quandrature in respect of each other, said means having a first output for said first signal and a second output for said second signal;

a controllable amplitude modifying device having a signal input coupled to said second output, a control input and a third output;

n fixed gain amplitude modifying devices having respective inputs, coupled in parallel, to one of said second and third outputs, and respective outputs;

n respective adders having respective first inputs coupled respectively to said outputs of said it fixed gain modifying devices, respective second inputs coupled to that one of said second and third outputs which is not coupled to said it modifying devices, and respectives outputs;

respective frequency multipliers producing frequency multiplication by p, having respective inputs coupled to said adder outputs and n outputs supplying respectively said reference signals;

and control means for controlling said controllable amplitude modifying means, said control means having an output coupled to said control input.

For a better understanding of the invention and to show how the same may be carried into effect, reference will be made to the drawings accompanying the ensuing description and in which:

FIGS. 1, 2 and 3 illustrate by way of a reminder, a known modular antenna and the essential elements of examples of active modules, with which the invention is concerned;

FIGS. 4 and 5 illustrate respectively block diagrams of two circuits for generating reference signals in an electronic-scan antenna using active modules, in accordance with the invention;

FIG. 6 is an explanatory diagram and FIGS. 7 and 8 are general block diagrams of improved electronicscan antennas in accordance with the invention.

Throughout the description, like references are used for denoting like elements Known electronic-scan antennas with active modules, operating at a frequency F, essentially comprise a master generator P, FIG. 1, producing a pilot signal S of frequency F, n generally identical modules, M,, M,, ..M,., and n phaseshift devices D,...D,...D,.. In certain antennas, the phaseshift devices are incorporated in the respective modules with which they are associated. In all cases, a phase computer C, or a memory device, supplies to n phase control devices C to C,,, the values of the phases to be applied to devices D D,, respectively, as a function of the angle 0 of the radiation direction.

Whether they form an integral part of the modules or not, or, again, are constituted by phaseshift devices or by diode logic systems, the phaseshift elements D, (i 1, 2....n), in all cases, supply n respective reference signals S S ..S,, of frequency F, which are phase shifted with respect to the master signal by d: ,(i 1,2 ..n), a quantity which may range between 0 and 2 1r.

Depending upon whether the modules incorporate oscillators or amplifier circuits, as power generators, the signal S and, consequently the signals S, (i l,2.....n), will have a higher or lower power, but in all cases they will have a very low power compared with that radiated by the modules.

In FIG. 1, continuous lines illustrate the coupling between the modules and the master generator, but, of course, the coupling could be effected by radiation in the case of modules including respective oscillators.

if the antenna is also used for reception, a duplexer located between the phaseshift devices and the receiver, ensures that the transmitted and receiver signals are correctly switched.

The invention relates to active module antennas in which the phaseshift devices are not incorporated in the modules themselves.

By way of reminder, FIG. 2 illustrates an example of a known active module in the case where simultaneous transmission and reception are possible the module then essentially comprises a transmitter oscillator OE of frequency F whose phase is controlled by a synchronisation signal SE of frequency F through a phase loop PE essentially embodying a phase detector DE and an amplifier AE the signals produced by the oscialltor OE can, if required, be amplitude-modulated by an external signal 2;

a local oscillator OR of frequency F, which differs from F whose phase is controlled by a synchronisation signal SR of frequency F through a phase loop PR essentially comprising a phase detector DR and an amplifier AR a mixer MR with one input coupled to the oscillator OR and another input coupled to the reception" terminal of the duplexer DR, which in turn is coupled to the antenna and to the oscillator OE.

The intermediate frequency signals at the output of the mixer MR are amplified in the amplifier Al which is coupled to the receiver R.

If transmission and reception are not simultaneous (which is the most general case), a single oscillator can be used as shown in the diagram of FIG. 3, where SW, and SW, are switches which are synchronised with the duplexer, and R, a grounding resistor for switch SW,.

The object of the invention is precisely the supply of the signals SE and SR; these signals are similar to the signals S, of FIG. 1.

The signals SE and SR are generally of the same power and may be possibly obtained from the same master generator.

In all cases, the signals 8,, whether used for transmission (signals similar to SE) or for reception (signals similar to SR), are obtained in accordance with the invention from a master generator output signal of lower frequencyfequal to F/p (F being equal to F, or F, as the case may be), and, a control device.

Respective intermediate reference waves S, of frequency F/p, are obtained for each module by the addition of two components which are in phase quadrature with respect to each other, the amplitude of at least one said components being modified (attenuated or amplified) as a function of the angle of the desired radiation direction (and this modification being the same for all the modules) and at least one of said two components being furthermore subjected to a fixed modification (attenuation or amplification) which is different for each module. The signals S, are then obtained from the signals S,'by frequency multiplication.

In the following for the sake of brevity, it is assumed that the amplitudes are only attenuated.

FIG. 4 illustrates the block diagram of a circuit for generating the signals S, in accordance with the invention A signal generator G supplies two component waves V, and V, of identical frequency f, which are phase-shifted with respect to each other by 17/2; for example, generator G may be an oscillator, of frequency f= l 15 Mc/s with outputs which are in quadrature, or be built up by an oscillator and a phase-splitter in series. The two component waves respectively illustrated by the vectors V, and V, in FIG. 6 are respectively applied to the input signals of amplitude modifying devices, for example variable-gain attenuators AV, and AV,, whose gain vary as a function of the desired radiation direction 0. To this end, a computer Ca, or a memory device (when the values of remains fixed) supplies, to the devices CG, and CG, controlling the gain of the attenuators, the appropriate gain value indication as a function of 6.

The output of the attenuator AV,, producing the signal K, V, and the output of the attenuator AV,, producing the signal K, V,, are coupled respectively to the inputs of an adder AD, the output of which is directly coupled in parallel to the inputs of n attenuators ATi (i l, 2.... n); the outputs of these attenuators ATi are coupled respectively to the first inputs ofn adders AD, (1' l,2...n); the respective second inputs of adders AD, are fed with signal V, (and, more generally, with one of signals V,, V,, K, V, or K, V,).

The outputs of the adders are connected to respective frequency multipliers X, (i l to n). For an odd value of n, the first input of the central adder [i n l/ 2 is not supplied and this adder can be discarded.

This phase-shifting method is of particular interest in the case of a transmit-receive antenna, since it is carried out simply by means of attenuators and adders,

that is to say elements which can be operated at two distinct frequencies.

It is recalled that the phase, in relation tg that of signal V,, of the signal (illustrated by vector V in FIG. 6) obtained by the addition of the two signals K, V, and K, V, varies between zero for K,=l) and 1r/2 for K, =0 as a function of K,IK,; l amplitude is equal to IV, V K, 2 where I V,| l V,| the phase of the signal obtained by the additon of signal V, to the latter sum multiplied by coefficient r, in the attenuator AT, is tan (K, r,/ 1+K, r,). FIG. 5 is the block diagram of a simplified embodiment of the invention it is assumed here that the two components are obtained by means of a phase splitter MD which is fed by a stable oscillator 0 and that the radiating elements of the modules are symmetrically arranged; since symmetrical elements are phase shifted by the same values of opposed signs (4:, the phase-shifts q), and are obtained respectively by means of the same signal in phase with the oscillator and of opposite signals in quadrature; therefore, the attenuator of signal V,, shown at AV, comprises two symmetrical outputs supplying the signals K, V, and K, V,. It is also assumed here that K,=l the variable attenuator of signal V, is discarded and signals K,V, or K, V, are directly applied to the inputs of the n attenuators AT,.

If n is even, the signals K, V, are applied to n/2 attenuators AT,....AT,,,, and the signals K, V, to the attenuators AT,,,, ,...AT,,. If n is odd, the signal K, V, supplies the attenuators AT,....AT,,, and the signal I(, V, the attenuators AT,,,,,,,,,...AT,,. Of course it is possible to form exclusively the signal K, V, as in FIG. 4 and then to use negative gain attenuators for half the attenuators AT,.

FIG. 7 is the most general block diagram of a transmit/ receive electronic scan antenna comprising active modules, in accordance with the invention.

Two identical assemblies E, and 5,, operating at different frequencies off, and f, =f, f, (or f, +f,-), f, being the intermediate frequency utilised, respectively supply the signals K, V,, K, V, and, as the case may be, K, V,, with the frequencies F, and f,.

The signals are applied to two sets of attenuators, adders and multipliers, B, and B,, having respective structures identical to the sets AT,, AD, AD, and X, of FIG. 4 or 5.

The outputs of the set B, are coupled to the transmission reference inputs of the modules M, and those of the set B, to the reception reference inputs of the latters.

A single reference input in each module is used if the modules are equipped with means for switching signals of frequency f, and f to appropriate circuits, or if it is not intended that the antenna carry out simultaneously transmission and reception in this latter case the antenna will be provided with a single set, identical to B, and B,, and a device for switching between E, and E,.

If f, does not exceed f, by more than about one-tenth of f,, it is also possible to utilise the same phase-splitter for the two frequencies f, and f;. as shown in FIG. 8 where a switch SW selectively couples oscillators O, and O, to the phase-splitter MD, which is coupled to a single circuit Bo comprising the various elements shown in FIG. 4 downstream the signal generator G or in FIG. 5 downstream the phase-splitter MD.

For example, in the case of an antenna system with n=37 modules, and a radiating frequency F 9,200

Mc/s, the frequencyfmay be taken equal tof= F/p /MQ/- For a maximum scan angle 4) Max 30, the maximum phase shift angle at frequency f is d) Max =[A (Ir-1) d/2]sin 19 Max, where d is the spacing between two adjacent sources and A the operating wavelength. Assuming d=0.56 A, d) Max= 1071' and the corresponding maximum phase shift angle at frequency f is a Max= Max/80= 225. g

In the case of a single controllable attenuator, for example AV the amplitude modifying coefficients r, are given by the relation t, a, r, K: where a 1 are the phase shift angles at frequencyf; for 9 Max, i.e., with r, l and m a Max, K2= t 0: Max for n odd, which is the case here a, (n 1-2i)/ (n l) a Max For a radiating direction defined by 6 where B 6 Max, the value a =l/80 [2 1r/)\ 18 056A sin 0]= 1r/4 sin 0 is computed, which gives 1,01, The computation of K: may be carried out for each desired value of 8 in a computer, for example a digital computer associated with the antenna and coupled to a dig ital analog converter which supplies a voltage which may be applied to the control input of a diode attenuator for example. The following table gives the values of the phase error due to the non linearity of the tangent using two controllable attenuators as described, and

shown FIG. 4; in this case I, a, (r, K )/(l r, K K and K satisfying the relation K,/( l+l(,) I, a it results that t, a, [r, (l+K,) t, a,,]/[l +r, K which is a function of K,.

10 Self-evidently, the invention is not limited to the embodiments described and illustrated here purely by way of example.

In particular, the second inputs of adders AD, in FIG. 4 can be fed as well with the signal K, V, as with the IS signal V the values of K,, K, and r, being then determined so that t aMax=Kzl2Kl and r m being then equal to [n K /K,( l+r,)] where two attenuators AV AV: are used; the method of producing reference waves in accordance with the invention, could also be combined with conventional phaseshift methods. by

grouping the modules; for example if n 9, the modules can be grouped in three, three waves of different phases can be derived from the wave of frequency f, and each of these dealt with in the manner indicated with reference to FIGS. 4 and 5.

What is claimed is:

1. An electronic scan antenna system, comprising n modules Mi (1 l, 2 n) and a circuit supplying the modules with n respective reference signals Si of frequency F said circuit comprising:

component signal supply means for supplying a first and a second component signal (V V,) of identical frequencyf= F lp, where p is an integer greater than one, said signals being in phase quadrature in function. for some values of i; respect of each other, said means having a first out- 1 max 225 max tbmax 01 Am A l m Mn n "K: on theoretical (deg) 8015a,

.304 0.879 .175 9 92 10 0.03 6 4 .315 .763 .152 a 65 8 15 .1 8 .210 .652 .130 7 4 r s .1 8 .222 .519 .107 61 s 25 .15 12 .1 76 .425 .0846 ,sLiL... 5 .2 115 .132 .319 .0634 3!) 2175 .15 12 .0875 .212 .0423 24 25 .1 8 .043 .104 .0207 1 18 125 .0? 515 a, for a scan ai'igle l9 9 Max with, r61 example a maximum phase shift Max b q) Max 1125 =a,. Then K, I a, 0.199. lg a, is computed with K, 0.199 and the values of r, of the fourth column, that gives the correspondant values of a, The seventh column gives the theoretical values of a, which are half the values of the second column. Then the two last columns give the phase shift errors A01, and Ada, 80Aaq. It may be seen put for said first component signal and a second output for said second component signal;

55 a controllable amplitude amplifying device (AV,)

having a signal input coupled to said first output, a control input and an output;

further adding means (AD) having a first input connected to said output of said controllable amplitude amplifying device (AV 1 a second input and an output,

:1 fixed gain amplitude modifying devices (AT,, AT having respective inputs, coupled in parallel, to said output of the further adding means (AD), and

respective outputs;

n respective adders (AD,, ADg) having respective first inputs coupled respectively to said outputs of said n fixed gain modifying devices, respective sec ond inputs coupled in parallel to said first output and respective outputs;

respective frequency multipliers (X., X, producing frequency multiplication by p, having respective inputs coupled to said adder outputs and n outputs supplying respectively said reference signals;

and control means (CO for controlling said controllahlc amplitude modifying means, said control means having an output coupled to said control input;

wherein said circuit further comprises further control means (CO having an output, further controllable amplitude modifying means (AV,) having a control input coupled to said output of said further control means, a signal input coupled to said second output, and an output connected to the second input of said further adding means (AD) and further comprising a circuit for supplying said modules with n respective reference signals of frequency F said circuit having a structure identical to that of said circuit suplying said signals of frequency F with the exception that said component signals supply means supply signals of frequency f, Fg/P.

2. An antenna system according to claim 1 wherein said component signal supply means of said circuits comprise respectively in series respective reference os cillators and respective phase-splitters.

3. An antenna according to claim 2, wherein all the elements of said two circuits are common with the exception of said oscillators, said antenna system further comprising a switch between said oscillators and said common phase-splitter, selectively coupling one of said oscillators to said phase-splitter 4. An electronic scan antenna system, comprising n modules Mi (i l, 2, n) and a circuit supplying the modules with n respective reference signals Sr of frequency F,, said circuit comprising:

component signal supply means for supplying a first and a second component signal (V V of identical frequencyf= F lp, where p is an integer greater than one, said signals being in phase quadrature with respect to each other, said means having a first output for said first component signal and a second output for said second component signal;

a controllable amplitude amplifying device (AV,)

having a signal input coupled to said first output, a

control input and an output;

further adding means having a first input connected to said output of said controllable amlitude amplifying device (AVl a second input and an output n fixed gain amplitude modifying devices (AT,, AT having respective inputs, coupled in parallel, to said output of said further adding means and re spective outputs;

n respective adders (AD,, AD, having respective first inputs coupled respectively to said outputs of said n fixed gain modifying devices, respective second inputs coupled in parallel to said second output, and respective outputs;

respective frequency multipliers (X X, producing frequency multiplication by p, having respective inputs coupled to said adder outputs and n outputs supplying respectively said reference signals;

and control means (CO1) for controlling said controllable amplitude modifying means, said control means having an output coupled to said control in- P wherein said circuit further comprises further control means (C62) having an output, further controllable amplitude modifying means (AV2) having a control input coupled to said output of said further control means, a signal input coupled to said second output, and an output connected to the second input of said further adding means;

and further comprising a circuit for supplying said modules with n respective reference signals of frequency F said circuit having a structure identical with that of said circuit supplying said signals of frequency F with the exception that said component signals supply means supply signals of frequencyf F /p.

5. An antenna system according to claim 4, wherein said component signals supply means of said circuits comprise respectively in series respective reference oscillators and respective phase-splitters.

6. An antenna system according to claim 5, wherein all the elements of said two circuits are common with the exception of said oscillators, said antenna system further comprising a switch between said oscillators and said common phase-splitter, selectively coupling one of said oscillators to said phase-splitter, 

1. An electronic scan antenna system, comprising n modules Mi (i 1, 2 ... n) and a circuit supplying the modules with n respective reference signals Si of frequency F1, said circuit comprising: component signal supply means for supplying a first and a second component signal (V1 , V2) of identical frequency f F1/p, where p is an integer greater than one, said signals being in phase quadrature in respect of each other, said means having a first output for said first component signal and a second output for said second component signal; a controllable amplitude amplifying device (AV1) having a signal input coupled to said first output, a control input and an output; further adding means (AD) having a first input connected to said output of said controllable amplitude amplifying device (AV1), a second input and an output, n fixed gain amplitude modifying devices (AT1, AT2 ...) having respective inputs, coupled in parallel, to said output of the further adding means (AD), and respective outputs; n respective adders (AD1, AD2) having respective first inputs coupled respectively to said outputs of said n fixed gain modifying devices, respective second inputs coupled in parallel to said first output and respective outputs; respective frequency multipliers (X1, X2 ...) producing frequency multiplication by p, having respective inputs coupled to said adder outputs and n outputs supplying respectively said reference signals; and control means (CG1) for controlling said controllable amplitude modifying means, said control means having an output coupled to said control input; wherein said circuit further comprises further control means (CG2) having an output, further controllable amplitude modifying means (AV2) having a control input coupled to said output of said further control means, a signal input coupled to said second output, and an output connected to the second input of said further adding means (AD) and further comprising a circuit for supplying said modules with n respective reference signals of freqUency F2, said circuit having a structure identical to that of said circuit suplying said signals of frequency F1, with the exception that said component signals supply means supply signals of frequency f2 F2/p.
 2. An antenna system according to claim 1 wherein said component signal supply means of said circuits comprise respectively in series respective reference oscillators and respective phase-splitters.
 3. An antenna according to claim 2, wherein all the elements of said two circuits are common with the exception of said oscillators, said antenna system further comprising a switch between said oscillators and said common phase-splitter, selectively coupling one of said oscillators to said phase-splitter
 4. An electronic scan antenna system, comprising n modules Mi (i 1, 2, ... n) and a circuit supplying the modules with n respective reference signals Si of frequency F1, said circuit comprising: component signal supply means for supplying a first and a second component signal (V1, V2) of identical frequency f F2/p, where p is an integer greater than one, said signals being in phase quadrature with respect to each other, said means having a first output for said first component signal and a second output for said second component signal; a controllable amplitude amplifying device (AV1) having a signal input coupled to said first output, a control input and an output; further adding means having a first input connected to said output of said controllable amlitude amplifying device (AV1), a second input and an output. n fixed gain amplitude modifying devices (AT1, AT2 ...) having respective inputs, coupled in parallel, to said output of said further adding means and respective outputs; n respective adders (AD1, AD2 ...) having respective first inputs coupled respectively to said outputs of said n fixed gain modifying devices, respective second inputs coupled in parallel to said second output, and respective outputs; respective frequency multipliers (X1, X2 ...) producing frequency multiplication by p, having respective inputs coupled to said adder outputs and n outputs supplying respectively said reference signals; and control means (CG1) for controlling said controllable amplitude modifying means, said control means having an output coupled to said control input; wherein said circuit further comprises further control means (CG2) having an output, further controllable amplitude modifying means (AV2) having a control input coupled to said output of said further control means, a signal input coupled to said second output, and an output connected to the second input of said further adding means; and further comprising a circuit for supplying said modules with n respective reference signals of frequency F2, said circuit having a structure identical with that of said circuit supplying said signals of frequency F1, with the exception that said component signals supply means supply signals of frequency f2 F2/p.
 5. An antenna system according to claim 4, wherein said component signals supply means of said circuits comprise respectively in series respective reference oscillators and respective phase-splitters.
 6. An antenna system according to claim 5, wherein all the elements of said two circuits are common with the exception of said oscillators, said antenna system further comprising a switch between said oscillators and said common phase-splitter, selectively coupling one of said oscillators to said phase-splitter. 